Drastic immunoreactivity changes between the immature and mature forms of the Sendai virus HN and F0 glycoproteins

The immunoreactivity of the Sendai virus HN and F0 glycoproteins was shown to mature before reaching the final form exhibited by the native mature proteins. The maturation process differed for the two proteins. The native F0 immunoreactivity was shown to be defined cotranslationally, and the addition of high-mannose sugar residues may represent the final step in defining the maturation of immunoreactivity. On the other hand, native HN immunoreactivity was slowly fashioned during the hour after the completion of protein synthesis. Although addition of high-mannose sugar could constitute a necessary step in this slow maturation process, it was shown not to be sufficient. Processing of high-mannose sugars and HN self-association in homodimers and homotetramers were investigated as possible steps involved in the slow maturation of HN immunoreactivity. They were found not to play a significant role. On the other hand, conformational changes presumably took place during the maturation of HN immunoreactivity. Drastic immunoreactivity differences were also demonstrated between the native and denatured forms of the glycoproteins. Possible implications of these results in defining the pathways of glycoprotein synthesis are discussed.